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Every thread in Reddit gets assigned an incrementing identifier in base 36. For example, this thread's ID is 14cc8h, or 67,760,369. Thus, as of the time this thread was created, there are about 68 million threads on Reddit.

In our typical numbering system, base 10, each digit in a number corresponds to a power of 10. Likewise, base 36 means that each digit corresponds to a power of 36.

By way of example, in base 10, the number 2947 can be written as a series of powers of 10 multiplied by the value of each digit:

2 x 103 , plus

9 x 102 , plus

4 x 101 , plus

7 x 100

or 2000 + 900 + 40 + 7.

When we have bases higher than 10, we start using letters for the "digits". For example, [10] can be represented as a, [11] is b, [12] is c, and so on.

Just to play devil's advocate for a bit, what if the links on here also dealt with CAPITAL letters, as well as lower case letters and numbers, making for a ... (ok, let me get my calculator here....) BASE 62 number?

The other way around, 67,760,369 to base 62 would be 4Ajzb. As a side note, someone in r/math posted the largest known prime number, which ran on for something like 100 or more pages. I wanted to visualize it better by putting it into a higher base notation so I could fit it on one screen, and decided to try and use as much of the millions of unicode symbols as I could.

What should have been an hour of programming became 4 hours of trying to determine whether a character looked unique from all the previous ones, for example A, symbol 46 or capital Latin letter A, versus Α, symbol 713 or capital Greek letter alpha, among other problems. My program progressed to the point that with about 20 minutes of hand editing I could make a unique set of symbols for base 1000, but even that would not be enough to fit the largest prime number on a page.

The number was so large that probably the best idea would be to use base 5 or 8, and just assign each pixel to a color, white black red yellow blue (green orange violet). Obviously more colors could be used, but at that point I think it would be too difficult to distinguish them.

I was going to say that just writing it as a power of 2 defeats the point of visualizing it - but then I realized that writing the number in binary would be 1 repeating for millions of digits. That's literally the whole number, and as a black and white visualization it would just be a big black area.

I would guess that the largest possible base gives you the shortest possible links. You could go to a larger base with special characters, but I'm not sure how many browsers can parse easily. You could go larger with capital letters, but that brings some usability problems in.

Preface - I do not work for reddit, so this is pure speculation on my part.

If you look at the URL of this post, you'll see that after "comments/" but before "/how_many_threads" there is a number - 14cc8h. Presumably this is some sort of incremental thread identifier. It appears to be "base 36" (as in any alphanumeric character a through z and 0 through 9 can be used).

Also, by looking at recent post history, I think that the order of the numbers goes 1,2,3...9,0,a,b,c,d..z.

So hypothetically, in order to be 6 digits (14cc8h), we have exhausted all of the 5 digit combinations. That would require (365 )-1 posts = 60,466,175 posts. That gets us up to thread 111111. To get from 111111 to 14cc8h, that's another
(4 * 364 + 13 * 363 + 13 * 362 + 8 * 361 + 18 * 360 ) threads
= 6718464 + 606528 + 16848 + 288 + 18 =
= 7342146
Added to our original number
= 60466175 + 7342146
= This is approximately the 67,808,321th thread on reddit.

Now this takes a lot of assumptions into account (most notably that I don't suck at math, which is a BIG assumption). But also that reddit at no point changed their numbering scheme so that it started at a certain number of digits, etc.

Your logic is spot on, but the math on this is not quite right: c is 12, not 13; and h is 17, not 18. I posted an answer here that I think might clear up the confusion and presents a (possibly!) simpler way of understanding it.

This current thread has an id of 14cc8h. 87 in base 36 is 295 in decimal (assuming 294 test threads). This thread is no.67760369 in decimal. So there have been 67,760,075 threads so at the time this thread was submitted. Unless comments share the numbering.